But for still a necessary condition for causation

The "but for" test is a useful starting point for determining whether a defendant's negligence caused or materially contributed to the harm suffered by the plaintiff.

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The New South Wales Court of Appeal decision in New South Wales v Mikhael [1] adds to the growing body of superior court authority which discusses the requirements for factual causation under s 5D of the Civil Liability Act 2002 (NSW) and affirms the place of the “but for” test in determining causation in negligence.

Facts of the case

The respondent was assaulted by a fellow student, identified as “T”, shortly after the conclusion of a high school French lesson, during which there had been some altercation between the students. The assault left the respondent with brain damage. [2]

The respondent alleged that the school breached its duty of care by failing to provide teachers with information as to T's propensity to violence, even if provoked by a minor event, based on an event 6 weeks earlier, in which T assaulted another student, Tom, after a touch football match at the same school. [3]

The trial judge found the appellant was negligent in failing to take adequate precautions to prevent harm to the respondent, awarding damages in his favour. [4]

On appeal to the NSW Court of Appeal

On appeal, the appellant argued that the trial judge erred by:

1. finding the appellant breached the duty of care; and

2. failing to undertake any analysis or make a finding as to causation. [5]

Beazley JA (with whom Allsop P and Preston CJ of LEC agreed) allowed the appeal, finding that although the appellant did breach its duty of care, the respondent had failed to establish factual causation.

The focus of this article is on the second limb of the challenge: the successful appeal on causation.

"… that the school's negligence in failing to provide Ms Edgar [the teacher of the lesson, and Head Teacher Welfare at the school] with the full details of the earlier assault, including the minor provocation that had caused it, was a necessary condition of the occurrence of the harm: s 5D(1)(a)." [6]

The respondent was required to establish that the probable course of events, had Ms Edgar been informed of T's propensity to a violent response with minimal provocation, would have prevented the harm to the respondent. [7] That is, but for the negligent omission (the breach), the harm to the respondent would not have happened. [8]

Had Ms Edgar been properly so informed, contended the respondent to the appeal, the appellant should and would have taken steps to ensure the respondent's safety including leaving the classroom to check whether T was in the vicinity and escorting the respondent to a position of safety. [9]

The court found that these steps were either not properly put to Ms Edgar (in which case the court could not rule upon them) or did not amount to any more than a series of possibilities which, if implemented might have averted the incident. [10]

In these circumstances, the court was not prepared to make a finding of factual causation in the respondent's favour.

“But for” and the causation inquiry

Much of the discussion on appeal focussed on the first limb of the causation inquiry under section 5D(1) of the Civil Liability Act: “that the negligence was a necessary condition of the occurrence of the harm (factual causation)”. As a majority of the High Court observed in Strong v Woolworths Ltd t/as Big W, [11] the determination of factual causation under section 5D(1)(a) is a statutory statement of the “but for” test of causation.

Despite criticism of the “but for” test in cases of omission, “the statute imposes that test as the first gateway to proof of causation”. [12]Although the “but for” test is not the sole criterion for causation (see Allianz Australia Ltd v Sim), [13] the “but for” test is (apart from exceptional cases) “the threshold test for determining whether a particular act or omission qualifies as a cause of the damage sustained” (March v E & M H Stramare Pty Ltd). [14] That “threshold” test “still holds good in Australia” (Amaca Pty Ltd (under NSW administered winding up) v Booth), [15] under both the statute and the general law.

Furthermore, referring to the judgment of the High Court in Adeels Palace Pty Ltd v Moubarak, [16]the court said:

"… unlike the position at common law, where “but for” causation was not always a sufficient test of causation, the statutory “but for” test is a necessary test, save for the exceptional test to which s 5D(2) applies [which was not the case here]." (Mikhael at [91])

The “exceptional case” involves the inquiry “in accordance with established principles” as to whether factual causation is established where negligence cannot be shown to be a necessary condition of the occurrence of harm (section 5D(2) Civil Liability Act). Those “established principles” to which a court must have regard likely include at least that:

(a) legal causation and causation in philosophy and science cannot be equated;

(b) the purpose of legal causation is to allocate responsibility for harm;

(c) where more than one (concurrent or successive) tortious acts is a potential cause of injury, the onus is on the plaintiff to establish (on the balance of probabilities) that the defendant's wrongful conduct caused or materially contributed to that harm (March v E & MH Stramare Pty Ltd; [17]Strong v Woolworths [18]).

Simply put, the inquiry for proof of factual causation requires that a particular posited cause be necessary (but not necessarily sufficient) for the occurrence of the harm. That is, on the balance of probabilities, the negligent act or omission caused the harm, either on its own, or as part of a set of other conditions together necessary for the harm (to which the negligence contributed (in a not insignificant way)).

Probabilities not possibilities

Advocates must be conscious of the forensic burden they confront in establishing proof of causation under section 5D(1) of the Civil Liability Act.

The question of causation must be viewed against the factual circumstances in which the duty of care was owed and breached. [19] The court may draw appropriate inferences from an established evidentiary base where there is no actual or direct evidence of the necessary causative connection. [20]

However, Mikhael follows recent superior court judgments in emphasising the need for something more than causal “possibilities” or hypotheses as to causation before the court will impose liability in negligence. This arises from a combination of the application of the “but for” test and the civil standard of proof requiring the court to satisfy itself on the balance of probabilities that causation is established.

As Beazley JA remarked in Mikhael:

“But for” causation requires the court to be satisfied that some such step, if taken, would, on the balance of probabilities, have adverted the harm suffered by the respondent. [21]

In Amaca Pty Ltd v Ellis, [22]for example, it was not proven that asbestos was a cause of (a necessary condition for) Mr Cotton's cancer. Importantly, as the court noted, “Knowing that asbestos can cause cancer does not entail that in this case it probably did”. Similarly, in Adeels Palace: “Recognising that changing any of the circumstances in which the shootings occurred might have made a difference does not prove factual causation”. [23] And, in Merck Sharp & Dohme (Aust) Pty Ltd v Peterson, [24] to say that the consumption of Vioxx was “in the mix” of possible causes was not enough to show that consumption was a necessary condition for the plaintiff's heart attack.

In the context of Mikhael, the respondent might have proved “but for” causation if there had been evidence that Ms Edgar would have acted differently on the afternoon the assault occurred had she been aware of the earlier incident. However, the absence of such evidence and the reliance on possibility and inference appear to have been fatal to his case.

Conclusion

Mikhael adds to the growing weight of authority on causation in negligence to cement the place of “but for” in the causation analysis. Whether or not the Civil Liability Act applies, the test provides a useful starting point for determining whether a defendant's negligence caused or materially contributed to the harm suffered by the plaintiff.

This article was first published in Australian Civil Liability, Volume 9 No 5, December 2012

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Clayton Utz communications are intended to provide commentary and general information. They should not be relied upon as legal advice. Formal legal advice should be sought in particular transactions or on matters of interest arising from this communication. Persons listed may not be admitted in all States and Territories.